Conventional research reports concerning the intestinal microflora in breast feeding infants and infants fed with artificial milk have indicated that bifidobacteria are useful for human health. It is now confirmed that the number of bifidobacteria is significantly decreased due to gastrointestinal disorders and aging; and that the promotion of the growth of intestinal bifidobacteria is effective for the inhibition of carcinogenesis, the suppression of intestinal putrefaction, prevention of infectious diseases and the like. Therefore, the selective growth of intestinal bifidobacteria is extremely meaningful from the respect of the management of health and the prevention and treatment of various adult diseases.
From such respect, the number of foodstuffs with added of bifidobacteria (fermented milk, yogurt, etc.) has been increased recently, and from the aspect of the production of these foodstuffs and the quality control thereof, the development of a selective medium specifically counting the number of bifidobacteria in these foodstuffs is of significance.
Regarding the substance promoting the growth of bifidobacteria, namely so-called Bifidus factor, a number of substances have been investigated and reported conventionally, including for example N-acetyl glucosamine contained in mother's milk Proc. Soc. Exp. Biol. Med., 90, 219(1955)!, peptide-related substances Am. J. Clin. Nutr., 32, 1428 (1974), Agric. Biol. Chem., 48, 2159(1984)!, Carrot extracts Japanese Journal of Agricultural Chemistry, 55, 499(1981)!, Chem. Phar. Bull., (Tokyo), 14, 1191(1966)!, Sugar-related substances Annual Bulletin of Tohoku Welfare University, 10, 313 (1986)! and the like.